如何对UITextField进行单元测试以查看是否为空

Question

我尝试对文本字段实施单元测试，以检查该文本字段是否为空，但出现错误Unexpectedly found nil while unwrapping an Optional value。我正在使用Guard，但我不知道自己在做什么错。

这是我的代码：

class AdminPanelViewController: UITableViewController {

// Func to insert data from TextFields into CoreData
    func insertProduct(){

        guard let productName = productNameTextfield.text, productName != "" else{
            SCLAlertView().showError(Constants.nameRequired, subTitle: Constants.messageNameRequired)
            return
        }
        guard let productCategory = productCategoryTextField.text, productCategory != "" else{
            SCLAlertView().showError(Constants.categoryRequired, subTitle: Constants.messageCategoryRequired)
            return
        }
        guard let productPrice = productPriceTextfield.text, productPrice != "" else{
            SCLAlertView().showError(Constants.priceRequired, subTitle: Constants.messagePriceRequired)
            return
        }
        guard let productDescription = productDescriptionTextView.text, productDescription != ""else{
            SCLAlertView().showError(Constants.descriptionRequired, subTitle: Constants.messageDescriptionRequired)
            return
        }

        let product = Product(context: context) // Start inserting in Core Data
        let productUUID = UUID().uuidString
        product.id = productUUID
        product.name = productName
        product.category = productCategory
        product.price = Float(productPrice)!
        product.prodDescription = productDescription

        appDelegate.saveContext() // End inserting and save the content in Core Data
        resetAllFields()
        SCLAlertView().showSuccess(Constants.done, subTitle: Constants.messageProductAdded)
    }
}


// UNIT TESTING

import XCTest
@testable import ShoppingLand

class AdminPanelViewControllerTests: XCTestCase {

    var collection: AdminPanelViewController!

    // Test if ProductNameTextfield is empty
    func testIfProductNameTextfieldIsEmpty(){

        guard let productNameTextField = collection.productNameTextfield else{
            XCTFail("Product name is required !")
            return
        }
        productNameTextField.text = ""

        XCTAssertEqual(productNameTextField.text, "Product name is required !")
    }

}

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